The present invention relates to a rubber composition for a tire.
The securement of steering stability and fracture strength (durability) other than low fuel cost performance is important for an SUV tire and a tire for a high grade vehicle requiring high durability (areas also including a severe heat area and a punishing road area).
Fracture strength relates to cutting resistance and separation growth resistance and a method for securing the fracture strength includes methods such as (1) silica is replaced with carbon black and (2) the content of filler is reduced and rigidity and crack growth performance lowered is compensated with a butadiene rubber including 1,2-syndiotactic polybutadiene crystals (for example, refer to the patent document 1).
However, both of the increase of E* and the reduction of tan δ cannot be satisfied by the method (1) described above and since the dispersibility of filler is and tan δ is easily deteriorated by the method (2) described above, both of the increase of E* and the reduction of tan δ is not adequately satisfied yet.
Further, the lowering of E* caused by the decrease of the content of filler can be compensated with the butadiene rubber including 1,2-syndiotactic polybutadiene crystals to a certain degree, but when the content of filler is excessively decreased, the lowering of the fracture strength is induced.
Further, although a rubber composition including a butadiene rubber modified with tin at terminal as a diene rubber component and including carbon black as reinforcing filler is disclosed in the patent document 1, silica is not adequately dispersed in the diene rubber component when carbon black is replaced with silica as the reinforcing filler in the patent document 1, and both of the increase of E* and the reduction of tan δ was not adequately satisfied.
[Patent Document 1] Japanese Unexamined Patent Publication No. 2006-63143